"I have never met a working girl who is so enthusiastic in her work. She is no beauty queen, but I found her 'girl next door' looks very sexy. Read two old reports on her before I went. However, in my opinion they do not do her justice."

- 'Field report' from punternet.com

Among the more surprising findings this week has been the revelation that over a 10-year period, the number of men in Britain who have paid for sex has doubled. In 1990, 5.6% of 11,000 men asked said they had paid for sex, but by 2000 the figure was over 9%. The study, published in the journal Sexually Transmitted Infections, suggests that the rising divorce rate, sex tourism and the increasing availability of commercial sex services may all help to explain the rise. However, the figures remain startling.

"I was surprised by how quickly the figure had gone up," says the study's co-author, Dr Helen Ward of Imperial College London. "Though there are more men in the potential user groups now." Ward notes that the study found the most frequent visitors to prostitutes were single men aged 25-34, men who had previously been married and were now divorced or widowed, and men who lived in London. She also suggests that the increasing popularity of foreign travel, for business, for pleasure, and for stag weekends, has meant that many men might pay for sex abroad. "Looking at the media," she says, "you do get the impression that it's much more common for men on a stag weekend to get a collective blowjob or whatever." There has also, Ward observes, been a change in the nature of the sex industry as a whole - it is bigger and better organised than ever before. Through her work in clinical services at St Mary's hospital in Paddington, Ward has witnessed first-hand the increasing numbers of women arriving in the UK to work in the sex industry. "In the mid-80s most sex workers were British," she says, "now around 80% of the women using our clinic are not British."

Build it and they will come, perhaps. However, even an increasing supply of women offering sex for money and an increasing number of men without a regular sexual partner cannot really explain why more men now feel comfortable with the idea of paying for sex. (The average price per visit to a prostitute in London is £154, according to punternet.com.) "My feeling," says Ward, "is there is a general and continual increase in the way sex is presented as something continually available; it's a commodity now, with lads mags, you see it more in films and so on. In all aspects of society it has become much more about what you want, when you want it, whether it's 24-hour shopping or whatever, and sex has become part of that - this idea of 'no strings sex' just increasingly fits in with the lifestyle."

Indeed, the shift in the British perception of sex over the past decade has been dramatic. It has moved beyond Page 3 titillation and drifted down from the top shelf to encompass lads mags, ready access to pornographic films, and an increased sexualisation of TV content both pre and post-watershed, from Hollyoaks to Footballers' Wives, not to mention music videos and song lyrics. Strip clubs have became a common sight on our high streets; women learn to pole-dance; we've been introduced to Agent Provocateur, while Ann Summers has become a multi-million-pound business. Celebrities are also far more candid about their sex lives; several, including footballer Wayne Rooney and TV presenter Jamie Theakston, have memorably been caught in brothels.

Arguably the biggest change, however, has been the internet. Sex, particularly the commercialised notion of sex, is so accessible, whether you wish to download pornographic images or perhaps contribute to websites where men post reviews of prostitutes, escorts and strip clubs from around the world. Yesterday, on the UK-based punternet.com alone there were 59,939 reviews, including "beerbelly's" appraisal of Debbie from south London: "Quite short and a little chubby." There is, of course, no crumb of embarrassment in such field reports; indeed it seems obvious that the reviewers get an erotic thrill from recounting their adventures.

Such websites also boast links to the homepages of escort agencies, massage parlours and prostitutes, among them Susie Swallows, based in South Pembrokeshire. "I'm 5'7" with short brown hair, hazel eyes, 36C, size 12 and in my mid-30s," reads her website, alongside a photograph of her, clad in stockings and high heels. "I cannot recommend Susie highly enough," says one of her reviews. "This lady is fun, frolicsome and super company!" declares another.

"I haven't seen a change in the number of men paying for sex," says Susie. "It's just the same, and they're just the same normal, decent men they've always been." Susie, who joined the trade seven years ago through her involvement with swingers clubs, is keen to stress the normality and respectability of paying for sex. "We're not streetwalkers," she says, "we're not those alcoholic druggies, we don't have pimps, we do it ourselves and the guys we see wine and dine us, and take us to the theatre and that sort of thing. It's not seedy. The guys are gentlemen. And we pay our taxes like everybody else."

Susie's clients range from 20- to 70-year-olds, some regular, others less so. "Some guys like to move on to a different girl each time," she explains. "They don't like to get attached." The frequency of their visits largely depends on whether their payday falls weekly or monthly. "Half my gentlemen are married," she says. "They pay for sex because their wives won't give it! A lot of the guys love their wives so much but it's physically impossible for them to have sex and so they come to us to get their relief. We're like marriage counsellors. They say, 'Please hold me, give me a cuddle.'" Other times, she says, men make requests they would feel uncomfortable making to their wives. "They ask us, we do it, and then they leave. It's a business transaction."

The plain fact is that sex with a prostitute is different from sex with someone you love. The frequent comparison is that it is the equivalent of dining out: easy, different, and you don't have to do the dishes. There is something about this idea that has the lingering and unpalatable taste of the theory that a woman can either be a madonna or a whore.

Despite the increasing numbers of women in the sex industry, despite Sex and the City, and fancy lingerie shops and the fact that more women now own a vibrator than ever before, society persists in believing the antiquated myth that men want sex more often than women, that women are more happy with a kiss and a cuddle from a Mr Darcy, and that, therefore men should be permitted this little weakness. Arguably, men are now keener to pay for sex because in a society that edges closer to gender equality, paying a woman for sex affords men a degree of the power they feel is diminishing.

An increasingly open attitude to sex should, of course, be applauded, and there is a very reasonable case for the decriminalisation of prostitution. What is dangerous, however, is that the sex industry as it exists is largely dictated by men for men. It seems preposterous that at a point in our culture where grown women readily wear T-shirts emblazoned with the word "slut", men feel they "have to" visit a prostitute to play out the sexual fantasies because they are too embarrassed to discuss these things with their wives. Is it not astounding that it is less shameful to visit a brothel than to tell your partner you'd like to try anal sex or see her dressed as a cheerleader? So what has really changed in 10 years? Our perception of men's right to sex has certainly altered, as has our idea of how available sex should be. The shame, perhaps even the illicit thrill in visiting a prostitute has diminished. Alas, it seems our perception of women and sex has not.